Quiz 4 should be ready to be released soon. It is time to start planning Quiz 5.
What features goes into Quiz 5 is determined by what features the community wants and what features we have development-time to implement.
Among other smaller improvements I will include these three features in Quiz 5(My development-time on these three features is sponsored by the Norwegian Digital Learning Arena):
1. Written answer that supports multiple correct answers
This might be a new question-type, or a modification of short-answer/long-answer. The difference is that in this question-type the author might add multiple correct answers.
Issue: http://drupal.org/node/833572
2. Take Quiz using javascript
Today all responses from the quiz taker is stored in the database. This makes quiz slower, less scalable and also adds a lot of data to the database that might not be needed. In quiz 5 we will add a feature for taking quizzes as self-tests using javascript. All scoring logic will be done using javascript. This will make quiz-taking a lot faster, it will make caching easier and it won't store unnecessary data in your database.
Issue: http://drupal.org/node/833596
3. Import and export
A lot of work have been done on the import export features for quiz, and we will continue improving the import and export features this summer. We will improve the interface between quiz and quiz_ei, and we will test and improve the import and export features against some learning management systems.
Issues: http://drupal.org/node/833612 and http://drupal.org/node/833618
A feature I hope to include
I wish I could include more big features to the list. A very popular feature request is "multiple questions on each page".
Issue: http://drupal.org/node/503228
So far we don't have development time to implement it. We might get it soon though. The three "accepted" features above will be sponsored by The Norwegian Digital Learning Arena and developed by the Norwegian e-learning company Amendor(the company I work for), we might also get some volunteer work on some of the above features, but so far we haven't got enough sponsored and volunteer development time to implement "multiple questions on each page". I do however hope that a new co-maintainer might be able to contribute the time needed to realize the "multiple questions on each page" feature as well!
Drupal 7
Quiz 5 will be a drupal 6 release, and it will only be a few months between Quiz 4 and Quiz 5. After that we'll probably start looking at Drupal 7. If someone wants to start working on a Drupal 7 port right now I will be happy to discuss how it best can be done. There is an issue for a Drupal 7 port here:
http://drupal.org/node/714072

Comments
Quiz core API
Also I think it is very important in the future that we focus on improving the API in the quiz core modules. We don't want the quiz project to collapse under its own weight. Instead we want it to provide a strong and flexible API for other modules to build on.